CODEWITHSUNDEEP
pythonlistdictionaryinterpolation
Thiru
Thiru

Reputation: 3373

Interploating list using python

I have set list of x and y, for example

x=[1,2,3,4,5,6]
y=[1,4,9,16,25,36]

and I need to find the y values for a set of u defined as

u = [[2,3,1],[4,2,1],[6,3,2],[2,4,5],[2,3,6]]

I am using this interpolation module. It is similar to the numpy interpolate

Currently, I follow:

v = [interp(x,y,u[i]) for i in range(len(k))]

Is there a way to circumvent the for loop, because It increases my computational time. I could rather spare my memory instead of time. My list size are very huge! I hope that inbuilt map function could be used, but not aware of how to use it.

Upvotes: 0

Views: 92

Answers (1)

Gareth Latty
Gareth Latty

Reputation: 89087

map() loops internally too - it just does it C-side where it is faster. However, you are already using a list comprehension, which also offloads to C and will probably be faster than map().

That said, there is an opportunity to gain speed and readability here by changing your loop:

v = [interp(x, y, i) for i in u]

In Python, we loop over iterators, not indices. By indirectly looping as you were, you will slow your looping down significantly. It also makes it far less readable.

As to using map(), it could be done using functools.partial() to make a function that calls interp() with x and y prefilled:

import functools
f = functools.partial(interp, x, y)
v = list(map(f, u))

However, as I said before, this will likely be slower, and is far less readable.

(I use the term C-side in this answer presuming you are using CPython, but in any other implementation, it will also be implemented more efficiently, using whatever lower-level options are available).

Upvotes: 3

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